The present invention relates to an oil separator for separating oil from blow-by gas of an internal combustion engine.
Internal combustion engines are equipped with a recirculation passage for recirculating blow-by gas to the intake passage. An oil separator is provided in such a recirculation passage to separate mist oil from blow-by gas (for example, Japanese Laid-Open Patent Publication No. 8-240114).
The oil separator has a box-like case the interior of which functions as a separation chamber for separating oil from blow-by gas. The case has a horizontally elongated shape. An introduction pipe is connected to the bottom wall of the case at a first end of the case in the longitudinal direction. A discharge pipe is connected to a side wall of the case at a second end of the case in the longitudinal direction. Also, an oil drain pipe is connected to the bottom wall of the case at the second end of the case in the longitudinal direction.
In such an oil separator, blow-by gas is introduced into the separation chamber through the introduction pipe. When blow-by gas passes through the separation chamber, the oil contained in the blow-by gas is separated from the blow-by gas. After passing through the separation chamber, the blow-by gas is discharged to the intake passage of the internal combustion engine via the discharge pipe. The oil that has been separated from blow-by gas in the separation chamber is returned to the oil pan via the oil drain pipe and is reused.
Although a large part of oil mist contained in the blow-by gas is separated from the blow-by gas when the blow-by gas passes through the separation chamber, not all the oil is separated from the blow-by gas. That is, some of the oil contained in blow-by gas flows into the discharge pipe together with the blow-by gas. The part of the oil mist that has flowed into the discharge pipe collects on the inner wall of the discharge pipe and is discharged to the intake passage of the internal combustion engine by the flow of the blow-by gas. This prevents the oil from being efficiently reused. A further improvement is therefore needed for preventing the amount of oil consumption from being increased and the use efficiency of oil from deteriorating.